This invention concerns apparatus for significantly reducing or eliminating unwanted diagonal image artifacts in an image displayed by a system employing intraframe signal processing techniques, for example.
A conventional television receiver, such as a receiver in accordance with NTSC broadcast standards adopted in the United States and elsewhere, has a 4:3 aspect ratio (the ratio of the width to the height of a displayed image). Recently, there has been interest in using higher aspect ratios for television receiver systems, such as 2:1, 16:9 or 5:3, since such higher aspect ratios more nearly approximate or equal the aspect ratio of the human eye than does the 4:3 aspect ratio of a conventional television receiver. Video information signals with a 5:3 aspect ratio have received particular attention since this ratio approximates that of motion picture film, and thus such signals can be transmitted and received without cropping the image information. However, widescreen television systems which simply transmit signals having an increased aspect ratio as compared to conventional systems are incompatible with conventional aspect ratio receivers. This makes widespread adoption of widescreen systems difficult.
It is therefore desirable to have a widescreen system which is compatible with conventional television receivers. One such system is disclosed in U.S. Pat. No. 4,816,899 of C. H. Strolle et al. It is even more desirable to have such a compatible widescreen system with provisions for enhancing or extending the definition of the displayed image so as to provide extra image detail. For example, such widescreen EDTV (extended definition television) system may include apparatus for providing a progressively scanned image. A system of this type is disclosed in U.S. Pat. No. 4,884,127 of M. A. Isnardi and R. N. Hurst, Jr. The system disclosed by Isnardi and Hurst employs signal time compression and intraframe processing of center and side panel image information.
It has been observed that intraframe processing of video image information can result in reduced diagonal edge resolution and produces unwanted jagged diagonal artifacts especially in still image areas. In accordance with the principles of the present invention, there is disclosed herein apparatus which assists to reduce diagonal image artifacts in still image areas.